Usually, a person needing to wear spectacles and having thus a prescription filled by an ophthalmologist goes to the premise of an optician for choosing the frame of the future spectacles. The future wearer of the spectacles may try several spectacle frames and finally chooses one of the tried frames. The optician orders a pair of lenses corresponding to the prescription. The lenses sent to the optician have been designed and manufactured according to optical criteria.
Depending on the service provided by the lens manufacturer, the optician may have to cut the lenses to the fit the spectacle frame the person has chosen or in case of “remote edging” service the optician receives the lenses already cut and only has to fit them in the spectacle frame.
The inner circumference of the openings of the chosen spectacle frame (e.g. the openings of the frame where ophthalmic lenses are intended to be mounted) can be measured very precisely by a measuring device, for example a mechanical sensor. More particularly, the openings of the frame include an inner groove and the characteristics of the groove (tilt angle with the openings, depth of the groove, etc.) can be measured by the mechanical sensor in a measuring room.
The measurements performed by the mechanical sensor on the chosen spectacle frame make it possible to order ophthalmic lenses which fit the chosen spectacle frame, on the one hand, and the wearer prescription, on the other hand.
According to the measurements performed by the mechanical sensor in the measuring room, the optician or the provider of ophthalmic lenses are able to:                determine the best semi-finished lenses for the wearer according to optical criteria, for example the wearer prescription;        edge and bevel the lenses to fit with the measurements performed on the chosen spectacle frame.        
In the sense of the invention a step of cutting the lenses according to a spectacle frame shape is called “edging” and a step of forming a bevel on an external edged of the lens is called “beveling.”
The lenses provider has to ensure that the provided lenses are adapted to the wearer prescription and to the chosen spectacle frame.
For example, the lenses provider has to ensure that the future lenses can effectively fit the chosen frame which may have particular openings and groove.
It will be thus understood that the measurements performed on the inner circumference openings of the chosen frame and the choice of the semi-finished lens are of great importance for the provider.
Usually, the selection of the semi-finished lens is based on optical criteria, such as the wearer prescription, optical comfort and the measured parameter of the spectacle frame are used for the edging and beveling steps.
In some cases, the edging and beveling step can be proceeded according not only to the measured shape of the spectacle frame but also according to esthetic criteria chosen by the wearer. For example, the esthetic criteria may implies having front face edges of the ophthalmic lens substantially abutting with front faces of the chosen spectacle frame when the ophthalmic lenses are fitted in the frame.
According to the esthetic criteria of the wearer and his prescription it is not always possible to meet both optical and esthetic criteria.
Usually the lens manufacturer will select the semi-finished lens according to the optical criteria and will grind a calculated design fitting the wearer prescription on the rear face of the semi-fined lens.
The person executing the edging and beveling steps, for example the optician, receives the ophthalmic lens and has to proceed to the edging and beveling steps according to the shape of the spectacle frame and to the esthetic criteria of the wearer.
Depending on the shape of the ophthalmic lens, it is not always possible to edge and bevel the ophthalmic lens according to the wearer criteria because of an improper lens shape (external shape of the lens, shapes of the front and rear surfaces of the lens, lens thickness, etc.).
For example, the bevel curve of the spectacle lens may be less steep compared with the curve of the frame, depending on the bevel position, and in this case the frame is deformed so as to be matched with the bevel curve. However, deforming the frame can result in an increase of the frame size beyond the values calculated when the bevel position was selected, and thus in deficiency of the outer diameter or edge thickness of the lens.
Such limitations result from the fact that, the semi-fined lens selection and the design of the lens faces do not take the edging and beveling step into consideration.